At the present time various types of lighting fixtures and devices are used when a line of light is desired for illumination. Such lighting is sometimes called a “light bar” or “light line” or “linear lighting” or “strip lighting” or “one dimension lighting”.
For example, fluorescent bulbs and neon lighting each may provide an elongated strip of light. Such light, especially neon lighting, is widely used is signs. However, both neon and fluorescent lighting are limited in certain applications and in difficult environments, such as sites if high vibration or frequent physical shocks.
LEDs (Light Emitting Diodes) are semiconductor electronic devices which convert electric energy into electromagnetic radiation at visible or near-infrared frequencies when their pn junctions are forward biased. Compared to gas-filled tubes, i.e. neon or fluorescent bulbs, for illumination they are physically sturdy and long-lasting. For these reasons, LEDs are frequently used in signs, such as EXIT signs, and in traffic signals, such as RED/AMBER/GREEN traffic lights. In addition, LEDs are sometimes used for low light illumination using battery power, in such uses as PDAs, cellular telephones and warning signs.
In one particular application, that of escalator “step off” light, fluorescent lighting has become the common light source although it has serious shortcomings. In this application illumination is required through the last tread of an escalator's moving stairway. It is often written into building codes. A fluorescent fixture is located beneath the face of the moving escalator stair and its light shines through the comb-like bars of the stairs as a warning. The constant vibration of the escalator tends to seriously shorten the life of the fluorescent bulbs. The bulbs themselves are inexpensive but the down-time and labor required to replace such bulbs at these difficult locations behind the stair face makes such lighting expensive.
Various United States patents and patent applications relate to the use of LEDs as a linear light and their use in escalator illumination. In U.S. Pat. No. 6,623,151 to Peterson an LED double light bar is used as a warning signal light. In U.S. Patent Application 20030095399 to Code et al, an LED is mounted in a fixture having reflective walls and a diffuser, the fixture having flat end surfaces so they may be placed end-to-end to create a light bar. In U.S. Pat. No. 6,173,517 to Eiber et al, a light line consists of a series of surface-mounted devices (SMD) which are LEDs. In U.S. Patent Application 20020006039 to Kind et al, a plural LED light source is formed by a mirror reflector, an ellipse or a parabola, for linear illumination. In U.S. Patent Application 20030174517 to Kiraly et al., LED printed wire board segments within a lighting fixture form a light line. The fixture includes a linear reflecting mirror and a window. U.S. Pat. No. 6,530,465 to Laych relates to an escalator having LEDs and polymer light pipes to illuminate escalator stairs for safety. In U.S. Pat. No. 5,613,758 to Kamschal et al., an escalator at selected points is illuminated by glass fiber optical conductors. The above-mentioned patents and patent applications are incorporated by reference herein.